BENOY little knowledge: What are the benefits of preloading for bearings

What is bearing preload? Generally, rolling bearings have a certain clearance under working conditions. However, in order to achieve a specific purpose, when the bearing is configured, the bearing is obtained with a certain internal load through a certain adjustment method and used in a state of negative clearance. This method of use is called pretensioning.

What are the benefits of preloading for bearings? For rolling bearings, proper pretensioning can have the following benefits:

1. Improve rotation accuracy. After the bearing is pre-tensioned, the internal clearance is eliminated, and each rolling element is subjected to a certain preload, and the ferrule is supported from all directions, which can improve the rotation accuracy, enable the shaft to be positioned correctly in the axial and radial directions, and improve the shaft , Such as the machine tool spindle bearings and measuring instruments.

2. Increase stiffness. The contact between the rolling element and the raceway is elastic contact, and the rolling element can be regarded as a spring. Bearings with clearance are supported by only a few springs in the direction of force. The pre-tensioned bearings are spring-loaded in all directions and have a certain amount of preload. The number of rolling loads under load is greater than when there is a game, so the stiffness can be improved. In ball bearings, the relationship between the contact deformation between the ball and the channel and the load is nonlinear. As the preload increases, the contact stiffness increases.

3. Improve the bearing life. After pre-tensioning, the number of loaded rolling elements is increased, and the load on each rolling element is reduced. At the same time, the load can be distributed more evenly on each rolling element, so the bearing life can be improved.

4. Improve the bearing's damping and reduce noise. Pre-tensioning makes a stable oil film between the rolling elements and the raceways, improves the damping between the rolling elements and the raceways, and can improve the dynamic characteristics of the support structure and reduce noise.

5. Improve the dynamic performance of angular contact ball bearings. In angular contact ball bearings that rotate at high speeds, proper pre-tensioning can prevent the steel ball from spinning in a gyro, prevent or reduce the revolving slip of the steel ball, and control the spin slip of the steel ball.

6, suppress chatter and friction and wear. The outer spherical bearing is actually a variant of the deep groove ball bearing, which is characterized in that the outer diameter surface of the outer ring is spherical and can be fitted into the corresponding concave spherical surface of the bearing seat to play a self-aligning role. Radial spherical bearings are mainly used to withstand radial and axial combined loads, which are mainly radial loads. Generally, it is not suitable to bear axial loads alone. It is used for chatter-free processing of low-roughness machining machines, or in mechanisms where friction and wear need to be controlled when starting and stopping frequently.

7. Control the slipping phenomenon of rolling body revolution and rotation. This type of bearing with spherical outer bearings also has a certain self-aligning design, is easy to install, has a double structure sealing device, and can work in harsh environments. The bearing housing is generally formed by casting. Mounted bearings are high-precision component products that are combined with grease-sealed deep groove ball bearings and bearing housings of various shapes. The bearing assembly can be directly mounted on the body of the mechanical device through several bolts. It has a self-aligning function and can be replenished with grease. It is a very easy to install and use product. Such as for radial thrust ball bearings used in high-frequency motors and cylindrical roller bearings on jet engines.

8. Compensate for wear during operation. The bearing will increase the clearance due to wear during operation. This situation can be compensated by pre-tensioning.